Power measurement device

Abstract

Provided is a power measurement device including a detection part configured to detect a supply current and a supply voltage from a commercial alternating current power supply, a frequency control part configured to transit a fundamental frequency by the supply current and the supply voltage to an intermediate frequency, a conversion part configured to generate a digital current value and a digital voltage value of the supply current and the supply voltage having the intermediate frequency applied from the frequency control part and transit the intermediate frequency to the fundamental frequency again, and a calculation/control part configured to calculate wattage using the digital current value and the digital voltage value, which are output signals of the conversion part.

What is claimed is: 
     
       1. A power measurement device comprising:
 a detection part configured to detect a supply current and a supply voltage from a commercial alternating current power supply; 
 a frequency control part configured to transit a fundamental frequency by the supply current and the supply voltage to an intermediate frequency; 
 a conversion part configured to generate a digital current value and a digital voltage value of the supply current and the supply voltage having the intermediate frequency applied from the frequency control part, and transit the intermediate frequency to the fundamental frequency again; and 
 a calculation/control part configured to calculate a wattage using the digital current value and the digital voltage value, which are output signals of the conversion part, 
 wherein the calculation/control part is further configured to use the wattage to calculate an effective power and an ineffective power using a phase difference between the digital current value and the digital voltage value. 
 
     
     
       2. The power measurement device according to  claim 1 , wherein the detection part comprises:
 a current detection part configured to detect the supply current from the commercial alternating current power supply; and 
 a voltage detection part configured to detect the supply voltage from the commercial alternating current power supply. 
 
     
     
       3. The power measurement device according to  claim 1 , wherein the frequency control part comprises:
 a frequency generating part configured to generate a carrier frequency; and 
 a frequency synthesizing part configured to synthesize the fundamental frequency and the carrier frequency supplied from the frequency generating part to generate the intermediate frequency. 
 
     
     
       4. The power measurement device according to  claim 1 , wherein the conversion part comprises:
 a first sigma-delta modulation part configured to convert the supply current having the intermediate frequency supplied from the frequency control part into the digital current value; 
 a first down converter configured to recover the intermediate frequency to a band of the fundamental frequency; and 
 a first decimation filter configured to remove a noise generated by the first sigma-delta modulation part. 
 
     
     
       5. The power measurement device according to  claim 1 , wherein the conversion part comprises:
 a second sigma-delta modulation part configured to convert the supply voltage having the intermediate frequency supplied from the frequency control part; 
 a second down converter configured to recover the intermediate frequency to a band of the fundamental frequency; and 
 a second decimation filter configured to remove a noise generated by the second sigma-delta modulation part. 
 
     
     
       6. The power measurement device according to  claim 1 , wherein a band of the intermediate frequency is a band which is not affected by DC offset and a flicker noise. 
     
     
       7. The power measurement device comprising:
 a detection part configured to detect a supply current and a supply voltage from a commercial alternating current power supply; 
 a frequency control part configured to transit a fundamental frequency by the supply current and the supply voltage to an intermediate frequency; 
 a digital current value generating part configured to receive the supply current having the intermediate frequency to sample the supply current into a digital current value; 
 a digital voltage value generating part configured to receive the supply voltage having the intermediate frequency to sample the supply voltage into a digital voltage value; and 
 a calculation/control part configured to calculate a wattage using the digital current value of the digital current value generating part and the digital voltage value of the digital voltage value generating part, 
 wherein the calculation/control part is further configured to use the wattage to calculate an effective power and an ineffective power using a phase difference between the digital current value and the digital voltage value. 
 
     
     
       8. The power measurement device according to  claim 7 , wherein the detection part comprises:
 a current detection part configured to detect the supply current from the commercial alternating current power supply; and 
 a voltage detection part configured to detect the supply voltage from the commercial alternating current power supply. 
 
     
     
       9. The power measurement device according to  claim 7 , wherein the frequency control part comprises:
 a frequency generating part configured to generate a carrier frequency; and 
 a frequency synthesizing part configured to synthesize the fundamental frequency and the carrier frequency supplied from the frequency generating part to generate the intermediate frequency. 
 
     
     
       10. The power measurement device according to  claim 7 , wherein the digital current value generating part comprises:
 a first sigma-delta modulation part configured to convert the supply current having the intermediate frequency supplied from the frequency control part into the digital current value; 
 a first down converter configured to recover the intermediate frequency to a band of the fundamental frequency; and 
 a first decimation filter configured to remove a noise generated by the first sigma-delta modulation part. 
 
     
     
       11. The power measurement device according to  claim 7 , wherein the digital current value generating part comprises a first high pass filter formed between the first sigma-delta modulation part and the first down converter to remove the noise generated by the first sigma-delta modulation part. 
     
     
       12. The power measurement device according to  claim 7 , wherein the digital voltage value generating part comprises
 a second sigma-delta modulation part configured to convert the supply voltage having the intermediate frequency supplied from the frequency control part into the digital voltage value; 
 a second down converter configured to recover the intermediate frequency to a band of the reference frequency; and 
 a second decimation filter configured to remove a noise generated by the second sigma-delta modulation part. 
 
     
     
       13. The power measurement device according to  claim 12 , wherein the digital voltage value generating part further comprises a second high pass filter formed between the second sigma-delta modulation part and the second down converter to remove the noise generated by the second sigma-delta modulation part. 
     
     
       14. The power measurement device according to  claim 7 , wherein a band of the intermediate frequency is a band which is not affected by DC offset and a flicker noise.